1. Field of the Invention
This invention relates generally to a closed loop vapor cycle refrigeration system, and more particularly to a refrigeration system utilizing an engine-compressor device that is driven by high pressure gas in the refrigeration system.
2. Descrintion of the Related Art
Devices such as expansion engines have been used in vapor cycle refrigeration systems in an effort to improve the overall efficiency of such systems. For example, each of the U.S. Pat. Nos. 3,934,424, 4,170,116, 4,086,772, 4,094,169 and 4,208,885 teaches the use of an expansion device in a vapor cycle to improve the overall efficiency of the refrigeration system. However, such devices have failed to significantly improve overall efficiency of refrigeration systems because those systems do not either properly control the flow of the refrigerant through the evaporator or that such expansion devices are not efficient or the combination of both. Therefore, such prior art refrigeration systems have failed to gain commercial acceptance. Also, the art, in general has taught against the use of devices, such as expansion engines in refrigeration systems. For example, David Mooney in the textbook, Mechanical Engineering, states that "in actual cases, after allowing for the irreversibility of the real engine process, the gain by use of the expansion engine is usually negligible and such machines are not used in modem vapor refrigeration plants."
In a closed loop refrigeration system, a small amount of potential energy is stored in the pressure difference of the refrigerant between the high pressure side and the low pressure side. Energy is wasted when this potential energy is changed into kinetic energy in the expansion valve of the refrigeration system. Also, a larger amount of energy is stored in the liquid refrigerant temperature on the high pressure side, which is changed into kinetic energy of the molecules when the liquid refrigerant boils in the evaporator. The prior art refrigeration systems attempt to improve the efficiency by utilizing this kinetic energy to drive or operate an expansion engine, which in turn is used to perform some useful function. However, as noted above, these prior art systems do not overcome the energy waste because these system either do not properly control the expansion throttling process or the flow of the refrigerant through the evaporator or that these devices themselves are not efficient.
The use of an expansion device, such as an expansion engine, as taught in prior art systems produces an inherent conflict, which can be understood by considering the following two extremes of the flow of the refrigerant through the evaporator.
In the one extreme, if the refrigerant leaving the expansion engine is completely vaporized, there will be little refrigeration accomplished by the system.
In the other extreme, if liquid refrigerant is allowed to enter the compressors, unnecessary load will be placed on the expansion engine causing a loss of efficiency or mechanical failure.
The present invention provides refrigeration systems wherein the engine of the engine-compressor device coupled to the evaporator of system is driven by high pressure gas in the system. The engine in turn drives the compressor, which compresses the low pressure gas refrigerant from the evaporator. A novel and efficient enthalpy-expansion-jet-compressor for use in refrigeration systems is also disclosed. For convenience, the enthalpy-expansion-jet-compressor is referred to hereinafter simply as the jet compressor.